Each year some number of hikers, boaters, skiers, and outdoor enthusiasts encounter some difficulties that require emergency assistance. Some become lost while others are injured, bitten or succumb to the deleterious effects of unexpected bad weather. An extremely small number of these unfortunate people carry sophisticated radio equipment in the event they need to call for help. The vast majority, however, are relatively unprepared if disaster strikes and must rely on being rescued by paramedics or search parties. If those in need are stranded at night without a two-way radio, a fire, or a flashlight of some kind to indicate their position, rescue efforts can consume precious additional time and lives may be threatened.
A few partial solutions to the problem of locating persons who are lost or incapacitated outdoors include common flashlights or hiker's mirrors. These devices are limited, however, because they require some action to be taken by the user once some trouble or peril is encountered. If a hiker falls and becomes caught or unconscious, or if a boater is thrown into the water with only a life-preserver, it may not be possible to activate or operate some device that is designed to attract the attention of a rescuer flying overhead.
Some police, fire or paramedic rescue teams carry night vision equipment that is capable of sensing the body heat generated by people who require assistance. As an example, the Intevac Company of Palo Alto, Calif., markets "Generation III.TM." image intensifiers that can be used at night to detect heat sources. Many aerospace companies build complex and expensive night vision systems for use by the military. Hughes Aircraft Company manufactures a system called "Probeye.TM.", while GEC-Marconi sells a lightweight thermal imaging camera. Without a relatively bright infrared source that illuminates the position of those in need of rescue, the utility of this heat sensitive night vision equipment can be somewhat limited.
None of the night vision equipment described above offers an inexpensive, automatic and lightweight device which can help individuals in the wilderness attract assistance when they need it. The problem of providing a compact emitter that may be used as a location device has presented a major challenge to designers in the electronics business. The development of a simple and cost-effective apparatus that could be manufactured in large numbers and utilized by a wide variety of persons who venture outdoors would constitute a major technological advance and would satisfy a long felt need within the consumer electronics industry and emergency response management agencies.